[X86] Enable 8-bit OR with disjoint bits to convert to LEA

[X86] Enable 8-bit OR with disjoint bits to convert to LEA

We already support 8-bits adds in convertToThreeAddress. But we can also support 8-bit OR if the bits are disjoint. We already do this for 16/32/64.

Differential Revision: https://reviews.llvm.org/D58863

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355423 91177308-0d34-0410-b5e6-96231b3b80d8